Testing for gas in well drilling fluid



Aug. 14, 1962 E. J. DowER 3,049,409

TESTING FOR GAS IN WELL DRILLING FLUID Filed July 27. 1959 2 Sheets-Sheet l E. 70 wer INVENTR.

Aug. 14, 1962 Filed July 27, 1959 TESTING FOR GAS IN WELL DRILLING FLUID E. J. DowER 3,049,409

2 Sheets-Sheet 2 l-lllll V 4 l Z AIR 49 /y /W /a/ E. 0 wer INVENToR.

Afro/emga Unite States This invention relates to testing hydrocarbons contained in returning well drilling mud as an indication of whether earth formations being traversed have significant hydrocarbon content. More specifically, the invention deals with the use of a column of air as a carrier for hydrocarbon gases to be tested and mixed with hydrogen gas and then flared at a burner jet across an otherwise open gap in an electric circuit for completing `a current flow path by llame ionization of the organic components within the gap and the measurement of electric conductivity for determination of the characteristics of the hydrocarbon gas content.

When hydrocarbons are returned with drilling mud, an immediate indication of the fact is desirable, as is also a continuing record throughout the drilling operation of whether and how much hydrocarbons are being returned together with an occasional test of samples from productive Zones for determination and recordation of the constituency and proportionality of different components. F or such purpose, it is here proposed to employ a flowing column Iof carrier air for entraining hydrocarbons removed from returning mud and to mix the carrier air land any entrainments with a combustible inorganic gas for flame ionization. inasmuch as electrical conductivity of a flame burning organic substances varies according to organic substance content of the mixture, a measurement of conductivity affords convenient indication of the characteristics of the mixture.

An object of the invention is to provide simple and reliable mud logging instrumentation to be located at the drilling site and to use air for the surrounding atmosphere as the carrier `for samples of hydrocarbon substances withdrawn from returning mud and delivered lfor mixture with flame maintaining hydrogen intern-ally at a burner jet in advance of the iiame area and whose 'filame is projected across and closes a gap between spaced apart conductors in an electric circuit containing Ian indicator of llame conductivity.

A further object of the invention is to provide instrumentation as aforesaid wherein the indicator circuit contains a series of resistors and wherein voltage ydrop across various amounts selectively of the total resistance, changes the meter scale to suit volume variations of hydrocarbon content of the carrier air.

Another object of the invention is to provide for measurement of flame conductivity in one embodiment as a highly sensitive detector of air carried hydrocarbon volume and in another embodiment `for gas chromatography and in which a small sample of hydrocarbon gas before being mixed with hydrogen is passed with the carrier air through a separator from which the different components emerge in spaced time and discrete group relations for successive burnings to thereby show relative proportion of and the different components which make up the hydrocarbon sample.

Other objects and advantages of the invention will become apparent during the course of the following specication having reference to the accompanying drawings wherein FIG. 1 is a `diagram showing indicator circuitry according to the invention and FIGS. 2 and 3 are schematic views respectively illustrating a gas detector system and fa chromatographic system usable singly or in combination one with another.

The gas detector arrangement of FIG. 2 consists of a atet 3,049,409 Patented Aug. 14, 1962 E icc co-operative assembly of several elements, most of which are gener-ally conventional in character. Thus, la suitable motor driven pump 1 has its suction side or inlet connected by a pipe 2 with a mixing chamber 3 |and has its pressure delivery or outlet side joined to a branch line 4 containing a control valve 5 and to a branch conduit 6 having Ia pressure regulator 7 therein whereby fluid is delivered to the rest of the system at a substantially constant and reduced pressure. Gas between the pressure regulator 7 and the outlet of the pump 1 can be exhausted or diverted either into the atmosphere or for use with other equipment, as, for example, with the `system shown in FIG. 3, as will later be referred to.

The How path Ibeyond the pressure regulator 7 divides into two branches S and 9 and the branch 8 contains a filter 1t) to remove foreign particles and impurities from the air stream flowing through the branch and which lair is delivered to the burner cell 11 for purging purposes. The burner cell 11 comprises a cup shaped body of nylon, ceramic or other suitable electric nonconductive and tire resistant material and protectively encloses the *llame provided by burning fuel delivered through a small jet nozzle l2 forming an upper extension of the vertical leg 13 of a hollow T-coupling whose internal `space provides a mixing chamber for gases delivered to the interior thereof through the side legs 14 and 15 of the T-coupling.

Flame supporting fuel delivered through the leg 14 according to the present invention consists of a 'const-ant supply of hydrogen gas. Bottled hydrogen gas delivered at a controlled rate can be used but more conveniently yhydrogen gas can be generated at an electrolytic cell whose electrodes `are contained in a switch controlled electric circuit 17. Any power source, inclusive of a storage battery unit, supplies current, and an ammeter in the circuit provides a reading of the generation rate as controlled, if desired, by an adjustable rheostat. Hydrogen generated at a constant rate is collected at the top of the cell and `directed through a conduit 18 and a dryer 19 to a conduit 20 coupled to the burner jet branch leg 14. The other branch leg 15 of the jet burner is connected throu-gh a filter 21 and preferably a ilow meter 22 and a control valve 23 with the air column delivery conduit 9. Each of the iilters 10 and 21 consists of `suitable lengths of conduit packed with material, such as ybrick dust, to filter out dust particles but not the light hydrocarbon gases before the pressure air reaches the burner cell 11.

Entry of air into the system at the pump inlet is through either one of a pair of intakev conduits 24 and 25 controlled `by a multiple-way valve 27 leading to the mixing chamber 3. Between the multiple-way -valve 427 and the intake 25 is `a trap 26 arranged for the flow therethrough of drilling mud returning from the well and wherein any well gases can separate from the mud stream and lbe entrained in the air stream flowing through the trap when the valve 27 is properly set for the intake by pump suction of air through the inlet 25. For comparison of instrument recordings and to enable compensation for the presence at a well drilling site, of hydrocarbon gas in the free atmosphere adjoining the intake 25, the Avalve 27 can be set temporarily for induction of free air through the trap by-passing intake 24 lat a point immediately adjoining the trap intake 25. In either event, the column of air with or without hydrocarbon gases entrained therewith will be moved by the pump at a given pressure level as controlled by the regulator 7 to the burner jet and immediately in advance of the jet nozle will be mixed with the constant supply of hydrogen for flaring in the cell 11 for a continuous flame. Electrical conductivity through the flame will vary according to the content of organic gas within the carrier air and measurement of current will give a reflection of the absence or 3 presence of hydrocarbon gas and the relative amount of hydrocarbon gas.

The current ow measuring circuitry as diagramed in FIG. 1 involves a gap or break in the circuit provided by mounting a conductor terminal or pole 28 on the wall of the cell 11 to end in spaced apart relation with the tip of the burner jet 12. The burner jet constitutes a cao-operating conductor and is connected by a wire line 29 to one end of a series of resistors 43 and to a terminal of a current ilow or balanced input recorder 30. The other terminal of the recording indicator 30 is joined by a conductor wire 31 to -a selector switch 34 associated with the resistors 43 and one side of a battery 32 as a source of current and a conductor wire 33 connects the other side of the battery with the cell conductor 28 for completing the circuit except for the open gap between the ends of the conductors 28 and 12 and which gap is to be bridged by the burning llame.

Variations in amounts of organic content of burning gases varies conductivity in the electric circuit and readings at the indicator 30 can be translated into hydrocarbon content volume. Zero readings will obtain with a burning flame supported by an inorganic gas along with carrier air which is free of hydrocarbon gas but any addition of hydrocarbon gas will be sensed or detected with the system of FIG. 1, since circuit conductivity will increase in relation to volume increase of hydrocarbon particles burned in the tlame. For varying indicator scale or the meaning of its graduations and the response range of its co-operating pointer or marker to suit small concentrations as well -as larger volumes of hydrocarbon gases, there is contemplated a manual setting of the selector switch blade 34 for co-operation with any of the several contacts 3S, 36, 37, 38, 39, 40, 41, joined to diterent parts of the resistance 43, whereby voltage drop can be measured across the whole or any selected amount of resistance in relation to the hydrocarbon gas volume being burned at any time. At the start of a drilling operation and until a gas showing is obtained, the switch blade preferably is set at contact 35 and the marker will have an extended range `of movement whenever any small amount of gas becomes entrained in the carrier air. When and if hydrocarbon volume increases in the carrier air, the distances of indicator marker travel to indicate a given -amount of hydrocarbon content can be stepped down, in suitable relation to reduction in current ow resistivity in the llame, by shifting the selector switch to the other contacts 3641 in progression.

By way of example, the attenuation steps attainable with the selector switch are on the order of one, three, ten, thirty, one hundred, three hundred and one thousand for a particular installation in which a three hundred volt direct current source of current or battery was employed and the total resistance across the element 43 was on the order of three megohms. The conductor pole 28 was a platinum wire in line with the bore of the jet nozzle 12, resembling a twenty gauge hypodermic needle, yand was mounted to provide a gap of three-sixteenths of an inch. Regulated pressure of the air column ahead of llow resistance from a six-inch long lter 21 was maintained at approximately two pounds per square inch for a small tow rate, on the order of one-tenth to two-tenths cubic foot per hour. -All hydrogen generated was conducted to the cell and at a constant small rate at less than one pound per square inch and maintained combustion when mixed with the air.

The resulting sensitivity was quite high. In the absence of carbon particles, llame resistance was so high that practically there was no current ow. Plame resistance decreased and more current llowed in the measuring circuit as carbon content was added and ionized by llame heat. It was found that 0.01 percent hydrocarbon gas in the carrier air produced a voltage across the three megohms of tenmilliovolts. A mixture of 0.001 percent hydrocarbon gas in the carrier air produced one l millivolt, which is only one-tenth of the full scale of the usual recorder, or, in other Words, ten minor divisions of a zero-to-one-hundred chart. Accordingly, each chart division on the most sensitive scale is equal to one part per million of gas in the air.

To enable field use of more sensitive scales, a bias voltage supply has been added to the attenuator circuit. Thus in FIG. 1 there is shown connected at opposite ends of the resistance element 43 an electric circuit including a 1.35-volt battery 44- whose positive side contains a variable resistance 45 to provide a total of ten megohms resistance and whose negative side includes a balancing resistance 46 with a central take-off line through a resist- `ance element 47 whose resistance value may vary between one hundred and two hundred megohms, depending on the amount of zero control needed. The addition of the biasing supply allows the recorder to `be zeroed even though a continuous background level of several hundred parts per million exists. The adjustable bias voltage is opposite in polarity to the signal voltage and acts across the whole attenuator resistance. It follows that if a background level is balanced out on the times-one range, the attenuator can be shifted to any other range and the recorder remains at zero. Should the recorder read sixty chart divisions on a times-one chart, the attenuator can be moved to the times-three range to move the recorder to the correct value of twenty chart divisions. Such zero control affords accurate recording of small variations in concentration on the order of twenty to thirty parts per million change when normal level of concentration may be two hundred parts per million.

To check and correct for the effect of gas-laden air at the point of intake 25 into the system, the valve 27 should be shifted for the intake of air in by-passing relation with the trap 26 for enabling the elect of hydrocarbon gas in the atmosphere to be zeroed out on the recorder and to give a true measurement of gas picked up from the mud by carrier air from surrounding atrnosphere in normal operation.

In the arrangement of FIG. 3, the pump 101 or any other -suitable source of compressed air leads through a pressure regulator 107 to the two branches 108 and 109. The branch 108 supplies purge air to the cell 111 and preferably includes a -flter 110. The air column line 109 leads through a multiple-way valve 48 which in the full line position of the valve parts illustrated directs the carrier air stream through a line 49, a sampling chamber and a chromatograph column 51 to one branch of the jet burner. The other branch of the jet burner receives |hydrogen gas `from an electrolytic cell 116 after passage through a dryer 119 for a continuous burning within the cell 111 and co-operation with the electric circuit, as previously discussed in connection with FIG. l. A sample of gas can be injected for carriage by the air stream to the burner jet in either of two ways. For a comparative or calibration test, a known sample of measured quantity contained -in a hypodermic needle can be injected manually at the box 50 after the needle punctures a rubber diaphragm constituting one of the walls of the box 50. A practical installation contemplates the use in tandem of the detector system in FIG. 2 with the chromatograph system of FIG. 3, which is to say that the by-pass 4 immediately beyond the pump 1 is joined by a pipe connection with a conduit 52 leading to the control valve 48. By such connection, the conduit 52 is coupled with and is a continuation of the branch conduit 4 without altering the operations of either the detector system or the chromatograph system. The detector system will continue to function as previously described whatever may be the position of the control valve 48, as will now be referred to. This control valve 48 is illustrated as a rotor having three separate passages 53, 54 and 55 therein and being shiftable periodically between two different positions, one indicated by full lines and the other by dotted lines. In the full line position, pressure air moves aafla/ics from conduit 109 to conduit 49 through lthe valve passage 53, while valve passage 54 communicates the branch conduit 4 and its continuation supply pipe 52 through a pipe loop 56 of predetermined volume and valve passage 55 to an exhaust conduit 57. Tthe carrier air and its hydrocarbon content entrained at the chamber Z6 now passes through the loop 56 to atmosphere but at any instant the content of the loop is available a-s a sample amount for performance thereon of a chromatograph test. The pipe loop 56 can be of any desi-red length and volume so that when the rotary valve 4S is shifted clockwise in FIG. 3, to its second position the passage 5S will directly connect the inlet 52 with the exhaust S7 -while the valve passage 53 joins the air supply conduit 109 with one end of the sample containing loop conduit 56 and the valve passageway 54 connects the opposite end of the conduit 56 with the pipe 49 leading to the jet burner.

Whatever -the gas content of the sample air previously supplied `from Ithe trap` 26 by the pump 1 and through the line 4 of FIG. 2 and into the sample loop conduit 56, such air and its content will constitute a given volume sample of gas to be analyzed and blown or pushed as a slug from the loop by the pressure column from conduit 109 toward the llame cell. In the flow of this sample slug through the chromatograph column 51, its components of hydrocargon gas will be separated one `from another and move Ito the Iburner in time succession and in .discrete groups so that, for example, the first or lightest component will leave the column 51 more or less as a batch, followed by succeeding distinct batches or" other progressively heavier hydrocarbon components in the order of methane, ethane, propane, isobut-ane, butane, isopentane, pentane, etc. Thus successive burnings of the intermittently eluted and individual hydrocarbon gases will be analyzed and recorded each in order of constituency and in terms of relative proportionality according to measured chan-ges yand durations in iiame conductivity.

The chromatographic column 51 can be in the nature 0f a long tube, such as twenty-two reet in length, packed with an adsorption type of material, of which an example is dimenthal-sulfolane on brick dust. For such column, the regulator- 107 -should be set vfor carrier air pressure of about twenty-two pounds to afford a flow rate of one-tenth to two-tenths cubic foot per hour.

As Ia safety factor, a simple thermistor bridge at the -iiame cell and a panel meter can be added to indicate cell temperature and whether the flame is burning and means provided to stop hydrogen generation and escape should the arne be extinguished. Also, a small ange 58 just below the jet tip serves to dissipate heat and prevent combustion inside the jet passage,

As Abefore indicated, the detector system for continuous automatic logging purposes and the chromatograph system for selective use in analyzing detected returns at will are usable separately of one another but preferably are intended for conjoint installation during the well drilling operation for recording a complete history of penetrated productive zones and their compositions.

What is claimed is:

l. In a system for determining the characteristics of hydrocarbon gases by burning samples of the same in a ilarne whose electric conductivity varies with differences in gas constituency, an electric circuit having a gap therein, means to measure current in the circuit, a gas burner projecting a flame across said gap, means to supply a continuous ow of hydrogen to said burner .for maintenance of the ame and other means lto supply to said burner a stream of air under pressure and comprising a conduit leading to said burner, an air delivery pump connected with the conduit and provided with an air intake connection, branch induction, passages coupled with said air intake connection, valve means controlling communication between the air intake connection and said passages, a gas trap for connection in a well mud line and provided with an atmosphere air entry opening 6 and joined to one of said passages for the withdrawal from the -trap of air and gas entrained therewith, the other of said passages extending to and having an atmos- .phere air entry opening adjacent the entry opening of said trap, said valve means being operable to open and close the respective passages selectively.

2. In a system of the character described, an electric circuit having a gap therein, means to measure current in the circuit, a jet burner to project a iiame across said gap, Ia ilame protective box yaround the jet burner, a combustible gas passage leading -to the yburner and having branch inlets thereto, a source of hydrogen connected to one of said inlets and supplying hydrogen fuel to the burner, a conduit connected to the other of said inlets for supplying air as a carrier `for any such organic gas as may be entrained within the carrier lair, a gas trap having an outside air inlet, a pressure pump having an outlet connection with said conduit and an inlet connection with ythe interior of said trap to withdraw air and trapped gas therefrom, means operable to close said inlet connection and open the pump inlet directly to outside air and a branch line passage leading from said conduit downstream from the pump and to the interior of said flame protective lbox in by-pass relation to the burner.

3. In a detector system of the character described, an electric circuit containing a current diow indicator and spaced apart conductors providing a gap therebetween, a lburner jet to project a gap bridging ame across the space between said conductors, means to supply llame supporting hydrogen to said burner jet, a hydrocarbon trap for connection in a well drilling mud line, means connecting the interior of the trap to atmosphere Ifor 4a-i-r entrance to the trap, a pump having its inlet connected with the interior of said trap 'and operable to continuously withdraw fair and hydrocarbons entrained therewith from the trap and means `delivering pump exhaust to said burner for combination with the hydrogen supply.

4. In a system for analyzing hydrocarbon content of returned well drilling mud, a mud return conduit including a hydrocarbon gas separation chamber, means connected with said chamber for flowing -air Ithrough the cham-ber as a carri-er to entrain gas, a pair of branch delivery lines receiving the carrier air and forming part of said means, a burner jet having a mixing pass-age Iand a pair of branch passages leading thereto and one of which branch passages is connected with one of said branch delivery lines, a supply of hydrogen gas connected with the mixing passage by the other branch passage leading thereto, an electric circuit having a pair of spaced apart conductors Whose intervening spac-e is bridged fby the Iburner flame for current ow which is variable according to the ratio of the hydrocarbon gas to the carrier air, means to indicate current flow changes as Ia detector of the presence of hydrocarbon gas in the air, a second electric circuit having a current lflow indicator and a gap in lthe circuit, a jet burner for projecting a flame across said gap, two pipe lines leading to the last mentioned jet burner, means to supply hydrogen gas through one of said pipe lines, sampling means connecting the Iother pipe line with the other of the aforesaid branch delivery lines and operable for supplying a given volume of carrier air and entrained hydrocarbon gas from said chamber to the jet burner and separator means in said other pipe line active to retard flow at differential rates of the different components of the air entrained hydrocarbon gas sample for the sequential burning of said components and a result-ant variation of current ow in said second electric circuit for chromatograph purposes.

5. `A method for testing gas in oil well drilling mud including separating organic gas from drilling mud and utilizing a stream of pressure air as a carrier of the separated organic gas, mixing the steam with hydrogen fuel adjacent a yjet burner, -burning the mixture at the jet burner, passing electric current across a circuit gapbridged by the burning flame and measuring current variation in 4 the circuit as indicative of characteristics of the organic gas entrained with the carrier air.

6. The method of analyzing hydrocarbon content in well drilling fluid return including passing a column of carrier air through a portion of the drilling uid return path for entrainment by the carrier air of hydrocarbons separated from the drilling uid, mixing the carrier air and any hydrocarbon entraiument therein with an inorganic uel and then burning the mixture and measuring electric conductivity of the burning mixture.

7. The method of analyzing hydrocarbons including mixing an air carrier column with hydrogen fuel and aming the mixture between spaced apart conductors in a current ow measuring circuit and introducing into the carrier air column and in upstream relation to its point of mixture with the hydrogen fuel the hydrocarbons to be analyzed and Whose burning in the ame provides a current flow path joining said conductors.

8. The method of claim 7 together with the additional step of passing the carrier air through a chromatograph column of adsorption material to separate said hydrocarbons according to their relative ow rates through said material.

9. The method of analyzing hydrocarbons returned with well drilling mud including separating from the mud and entraining separated hydrocarbons in a pressure air carrier stream, delivering the carrier stream and entrained hydrocarbons to a burner jet, constantly supplying the burner jet with hydrogen fuel to maintain a flame in which the carrier air entrained hydrocarbons are ared upon delivery across a gap between spaced `terminals of conductors in an electric circuit for the flow of current through the flame Whose conductivity varies in accord with organic content at any instant and measuring current conductivity of the ilame.

References Cited in the file of this patent UNITED STATES PATENTS 2,511,177 Richardson June 13, 1950 2,663,379 Doan Dec. 22, 1953 2,694,923 Carpenter Nov. 23, 1954 OTHER REFERENCES Ray: Nature, 180, 40B-405 (1957).

Henderson et al.: .T. Chem. Soc., pages 2299-2302, 1956.

Harley: Nature, 181, 177, 178 (1958).

Scott: Manufacturing Chemist, 29, 411-416 (1958). 

5. A METHOD FOR TESTING GAS IN OIL WELL DRILLING MUD INCLUDING SEPARATING ORGANIC GAS FROM DRILLING MUD AND UTILIZING A STREAM OF PRESSURE AIR AS A CARRIER OF THE SEPARATED ORGANIC GAS, MIXING THE STEAM WITH HYDROGEN FUEL ADJACENT A JET BURNER, BURNING THE MIXTURE AT THE JET BURNER, PASSING ELECTRIC CURRENT ACROSS A CIRCUIT GAP BRIDGED BY THE BURNING FLAME AND MEASURING CURRENT VARIATION IN THE CIRCUIT AS INDICATIVE OF CHARACTERISTICS OF THE ORGANIC GAS ENTRAINED WITH THE CARRIER AIR. 